Very large rectangular grid of lights. At about 1000' and moving silently

3/25/11 UFO Friday night 3/25/11 at around 11:00 pm. I was traveling westbound in a top down convertible at 75 MPH on Alligator Alley, (I-75) At around MM 51. There are no lights on this road. The highway is divided by a very wide grass median. Ahead of me, over the median came a very large square and very flat grid of lights. The grid was almost as wide as the median about a 100’ +or- and twice as long, like a football field. There were bright white marker light’s at evenly spaced intervals and lessor light’s making up a grid pattern within the square perimeter. I was moving at 75 and it appeared to be moving at about 100 +/-, eastbound, not faster. Altitude was about 1000’. It was silent.